1. Field of the Invention
The present invention relates to a capacitance type touch panel and a display device, and more particularly, to a technology effective for detecting disconnection of an X electrode or a Y electrode.
2. Description of the Related Art
A display device which includes a device for inputting information by a touch operation (contact press operation; hereinafter, simply referred to as touch) onto a display screen with the use of a user's finger or a pen (hereinafter, the device is referred to also as touch sensor or touch panel) is used for mobile electronic devices such as a PDA and a mobile terminal, various home electric appliances, an automated teller machine, and other such devices.
As the touch panel, there are known a resistive type touch panel that detects a change in resistance at a touched portion, a capacitance type touch panel that detects a change in capacitance, and an optical sensor type touch panel that detects a change in light intensity.
One example of the capacitance type touch panel is a touch panel disclosed in Japanese Patent Application Laid-open No. 2008-310550. In the disclosed touch panel, vertical detection electrodes (hereinafter, referred to as X electrodes) and horizontal detection electrodes (hereinafter, referred to as Y electrodes) are vertically and horizontally arranged in two-dimensional matrix, and the capacitance of each electrode is detected by an input processing portion. When a conductor such as a finger contacts with the surface of the touch panel, the capacitance of each electrode increases. The input processing portion detects the increase in capacitance, and calculates input coordinates based on a signal of the capacitance change detected by each electrode.
In the capacitance type touch panel disclosed in Japanese Patent Application Laid-open No. 2008-310550, one end portion of each of the X electrodes and the Y electrodes is connected to a wiring (hereinafter, referred to as extraction wiring), and the extraction wiring is connected to a terminal connected to a flexible wiring board, thereby supplying a drive voltage from one side of the Y electrode. Hereinafter, a touch panel of this type is referred to as an end-fed type touch panel.
In the end-fed type touch panel, for example, an AC signal is applied from the Y electrode, and the AC signal is detected from each X electrode. Based on the detected AC signal, the disconnection of the X electrode, the disconnection of the Y electrode, and the short-circuit between the X electrode and the Y electrode are detected.
In the above-mentioned method, however, the discovery of a disconnection failure at the other end portion of the X electrode or the Y electrode (the end portion which is not connected to the extraction wiring) is impossible in principle.
As countermeasures for discovering a disconnection failure at the other end portion of the X electrode or the Y electrode, it is conceivable to perform a test by bringing a probe into direct contact with the other end portion of the X electrode or the Y electrode. However, there is a possibility that another failure is produced in a manufacturing line process.